The goal of this research proposal is to characterise a potentially new target in metastatic breast cancer. Metastasis is the process by which cancer cells spread from the primary tumour site to secondary sites. Metastasis is of major clinical importance, since it is the main cause of breast cancer mortality. The target of study is the voltage-gated sodium channel (VGSC). VGSCs are found on cells in the nervous system and muscle. Drugs that target VGSCs are used to treat diseases such as epilepsy, abnormal heartbeat and pain. VGSCs regulate the migration of neurones in the developing nervous system. VGSCs also occur in metastatic breast cancer cells and regulate cell behaviours associated with metastasis, including adhesion and migration. The research project, to be carried out at the University of York, will study VGSCs in human breast cancer cells, mice and biopsy samples. We will test the hypothesis that VGSCs control metastasis in breast cancer cells by a mechanism similar to that in migrating neurones. Based on this work, it is possible that VGSCs may be a useful new diagnostic target in breast cancer. In addition, VGSC-targeting drugs may be effective for therapeutic intervention in breast cancer, to reduce and/or slow metastasis.

Technical Abstract:
The long-term goal of this research is to elucidate the functional role of voltage-gated Na+ channels (VGSCs) in breast cancer (BCa) metastasis. VGSCs exist as membrane complexes containing a pore-forming subunit with one or two subunits. Through the 1 subunit, which is an immunoglobulin (Ig) superfamily cell adhesion molecule, VGSCs regulate migration of neurones in the developing CNS in vivo. Recent work, largely restricted to in vitro models, has shown that VGSC and 1 subunits are expressed in metastatic BCa cells, and regulate cell behaviours associated with metastasis, including adhesion, migration and invasion. This proposal aims to test the hypothesis that VGSCs control cellular migration and invasion in metastatic BCa, by a mechanism that recapitulates neuronal signalling. In addition to using in vitro cell lines, I will develop an in vivo approach, using an established animal model and human biopsy material to characterise the expression and activity of VGSCs in metastatic BCa. I propose three specific aims. In Aim 1, I will investigate the mechanism of 1-mediated signalling in regulating the adhesion and migration of BCa cells. Specifically, I will test whether mechanism(s) underlying 1-mediated adhesion and migration in BCa cells may be analogous to those operating in neurones, using a combination of functional in vitro adhesion, migration and invasion assays, Western blotting and confocal immunocytochemistry. In Aim 2, I will investigate whether VGSC expression affects tumour formation and/or metastasis in nude mice in vivo. I will then test whether the VGSC-inhibiting drug phenytoin affects the tumour formation and/or metastasis. In Aim 3, I will determine whether VGSC expression and activity correlates with metastatic potential in human BCa tumour biopsies, using a combination of tissue microarrays, immunohistochemistry, realtime PCR, functional assays, Western blotting, confocal microscopy and patch clamp recording. The study will characterise VGSCs as new potential diagnostic and therapeutic targets in BCa, which is the most commonly diagnosed cancer in women, and the second-leading cause of cancer-related deaths. In particular, the study focuses on the process of metastasis, which is of major clinical importance, since it is the main cause of BCa mortality. Given that VGSCs are well established as clinical targets in the treatment of other diseases, such as epilepsy and pain, based on this work, it is possible that VGSC-modulating drugs already in use may also be effective in BCa therapy.